Air Pollution and Emergency Department Visits for Headache and Migraine

Associations between ambient air pollution and emergency department (ED) visits for headache and migraine were examined in a multi-city study during the period of April 2004 to December 2011 in nine cities across Ontario, Canada. Evaluate potential positive associations between air pollution and ED visits for headache. Data on ED visits for headache were retrieved from the national ambulatory care reporting system in Canada. Case-crossover design was used for this study for three diagnosis categories: migraine, headache-OS (other specified, OS) and headache-NOS (not otherwise specified, NOS). A time-stratified case-crossover technique was applied to investgate the associations of ED visits for headache with ambient air pollution. Odds ratios (ORs) and their corresponding 95% confidence intervals for ED visits associated with increased levels of air pollutants were calculated by applying conditional logistic regression. Among females, statistically significant positive results were observed for one unit increase in inter-quartile range (IQR) of NO2 (IQR = 9 ppb) for lag 0 days: OR = 1.015 (1.000, 1.030) for migraine and for NOS: for NO2 for lags 0 to 2, where the highest result was for lag 0: OR = 1.015 (1.005, 1.026), for SO2 (IQR = 2.5 ppb) for lag 2: OR = 1.012 (1.002, 1.021) and for PM2.5 for lags 1 and 2, OR = 1.011 (1.002, 1.021) and OR = 1.010 (1.000, 1.020) respectively among females. No significant statistically significant results were observed among males. Our findings support a number of statistically significant positive associations between air pollutants and the number of ED visits for headache and migraine.